Uncertainty Principle: A 4th Doctor ShortTrip
by That-Other-Doctor
Summary: Set between "The Seeds of Doom" and "Masque of Mandragora". I am Sarah Jane Smith, and I died on this day in my own future, many miles below an alien planet, far away from home.


"I want there to be no question of your current situation. In a few minutes of our planetary time, both yourself and your associate are going to be subjected to a series of physical stimuli which will cause a significant amount of discomfort in your nervous system. Do you understand the implications of this information?"

The Doctor's frown deepened the crow's feet in the corners of his pale blue eyes. They glowed in the near darkness. "As clear as proverbial glass. You're going to torture us."

Sarah Jane Smith hiccuped slightly, but didn't trust herself to say anything intelligible through her mounting fear. She sat in silence and gnawed her fingernails down to the quick. It was a detestable habit, but she had other things on her mind.

Their spokesperson did not smile or acknowledge the Doctor's brutal bluntness. He did not show any sign of sadism or pleasure. He was completely emotionless, and seemed resigned to remain that way, with the contours of his chalky grey skin pulled tight and rigid in a mask of concrete dispassion. "You are on the planet Ventrarius, designated Gamma Epsilon VII by your interplanetary survey committees. Specifically, you are being held in the Ventrarian Energy Core located two of your Terran kilometers beneath the capital city of Ventari. You are here because you are going to play a vital role in an operation designed to prolong the longevity of our species. You hold the keys to our survival."

"What sort of survival is worth torture and murder, dare I ask?" Sarah's tone was cold, but she couldn't completely hide the vein of terror in her words.

"Approximately five hundred Ventrarian years ago," the alien did not break form, "a frameshift genetic mutation was introduced to the Ventrarian DNA that resulted in a completely different coding sequence for a specific amino acid. Furthermore, the mutation altered the stop codon in the DNA translation in such a way that the mutation was very difficult to halt and to keep from spanning the generation gaps of the dominant humanoid species. There are no individuals free of the mutation currently living on Ventrarius."

The Doctor nodded slowly. "And what were . . . are, the effects of this frameshift mutation?" he asked.

"Our altered DNA codons remain unable to code for endogenous opioid peptides. Our entire planet is suffering from a massive strain of what you Terrans would refer to as depersonalization disorder. "

Sarah remained none the wiser, but the Doctor had pursed his wide mouth, his expressive face as grave as death.

"Hence the lack of emotion . . . the lack of anything, to be perfectly honest. Your bodies can't create their own neurotransmitters," said the Time Lord with no small amount of concern.

Sarah arched a slim eyebrow and looked pointedly at the Doctor. Even in the gloom of their cell, he could read the unspoken question on her lips.

The Doctor explained quietly, "The Ventrarians can't produce adequate, if any, levels of endorphins, Sarah."

"Oh!" exclaimed Sarah Jane, pleased to hear a word she could actually spell as well as fully understand. Her euphoria vanished as a sickening realization hit her like a cricket ball to the face. "Oh."

"Endorphins," the grey alien explained, his voice pancake flat with lack of emotion, "are short chains of amino acid monomers produced by the pituitary gland and hypothalamus of the brain."

Sarah's expression screwed into a glower strong enough to fry eggs. "I know what endorphins are, thank you very much. I did learn SOMETHING from my Aunt Lavinia. You can go stuff whatever venture you've got going on here right up your—"

If Sarah were one for whimsy, she would have said the native Ventrarian looked pitying, almost apologetic for the fact that she still suffered from such obstinate emotions as fear and anger. The Doctor shushed any more of Sarah's belligerence with a bony elbow in her ribs. She was about to fix her lethal stare on him, but the Doctor's expression was enough to make Sarah falter. Only someone who knew him as well as she did could have noticed the subtle changes: the minute tick right below his left cheekbone, the way his froggy mouth had suddenly turned bloodless from being clamped just a tad too tight.

The Doctor was frightened. Worse, he was uncertain, in the dark and ignorant of the scope of the Ventrarian menace. His trepidation had frozen his hearts mid-beat, locked his fingers in a grip that suddenly seemed very tight around Sarah's sore wrist.

"If you can't produce your own endorphins," she said carefully, willing her voice to remain level, "then that means you can't really stop FEELING anything."

"Excitement, physical exertion, love, Thai food," the Doctor's baritone voice dropped a notch and took on a sinister air, "and pain, create endorphins to produce an analgesic effect in the brain. The Ventrarians lost the appreciation of the aforementioned sensations a long time ago, when they became as deadly to the Ventrarian people as the Plague."

"Endorphin release is a vital biological function, one which we unfortunately lack," continued the alien. "Without the presence of endogenous opioid peptides, our bodies are unable to sate pain receptors from firing in our nervous system once a nerve impulse reaches the spinal chord. The result of which is an unrelenting torrent of nerve stimulation, trillions of pain receptors firing without interference. An injury as superficial as a paper cut brings as sure a death to a Ventrarian as a hail of bullets does to a Terran."

The Doctor twirled his fingers around the tassels of his absurdly long scarf, mulling the Ventrarian's words, and took his time in proffering an opinion.

"You _are_ in a spot of bother," he admitted after what seemed like an interminably long period of silence. Sarah pinched the bridge of her nose and shook her head incredulously.

"A species such as mine cannot survive under such circumstances. In order to ensure the continuity of our race, dire action must be taken."

Sarah took a deep breath and asked calmly, her eyes squeezed shut, "So when you mentioned that we were going to experience quite a bit of bodily discomfort, you're going to . . . torture us, in order to—"

"Harvest the amino acid monomers of our own endorphins," the Doctor finished quietly. His expression was grim, and that alone was enough to confirm Sarah's worst and most terrifying suspicions.

Her heart plummeted into her stomach. "Great. I thought it was actually something serious."

The Doctor patted the back of her hand with icy fingers. It wasn't much in terms of reassurance, but she was grateful, nevertheless.

"Does the idea of an end never justifying its means ring any bells?" asked Sarah bitterly, fixing the alien with the full measure of her fury and fear.

The Ventrarian barely blinked his goat-like eyes. "The idiom holds no meaning for me. It is irrelevant."

"Tell that to me in two hours time."

"I must consult my superiors," announced the Ventrarian, ignoring Sarah. "Then I will come for the female. You may prepare yourselves accordingly in the customs befitting your species."

The alien, having debriefed his prisoners, spun on a dime and left the Doctor and Sarah Jane's cell. As his oily olive robes swept out, the ovoid entrance telescoped shut like an aperture, and the world within the cell was plunged into absolute blackness.

Sarah closed her eyes, and then opened them again, but it made no difference. The darkness was strong enough to deaden her senses and warp her perceptions of space into meaningless parodies. If not for the floor beneath her feet, Sarah could have fooled herself into believing she was floating through the vacuum of deep space, about to have her bones crushed into powder, her eyes juiced like spoilt lemons, and her screams silenced in the void.

"Doctor!" she cried in a panic. Primal fear stopped her breath. She felt her lungs heaving, her throat constricting. Pearls of icy sweat beaded on her forehead, and the blackness in her line of sight began to bubble. She felt her blood boiling as she slowly but surely died in the vacuum of darkness.

"Sarah, calm down. You must not give in to panic." A venous hand clasped hers and held it uncomfortably tight. "Deep breaths, eh? In . . . and out. In . . . and out."

She breathed, allowing her chest to expand with generous doses of oxygen. The air whistled as she let it out through her nose. Her thundering heart slowed, and the fear-induced fog cleared from her mind.

The Doctor gave her fingers a squeeze. "Better?"

"Much. Don't know what came over me there."

"Mild claustrophobia. A total absence of light can have that effect on some people."

"But not you, I'm guessing."

"Erm . . . I'm afraid I'm not faring any better, Sarah Jane. I can't see a dicky bird."

She snorted, "Terrific. Here I was hoping you had some sort of a plan for getting us out of this hellhole before our little sadist friend comes back."

"Now that you come to mention it—"

"Yes?" asked Sarah hopefully.

"I've got nothing. Zilch. Nada."

She rolled her eyes heavenward, though for all the visual difference it made she may as well have left them staring straight ahead. For all of her exasperation, though, she did not give in to despair. The Doctor was one for playing the fool, even for her benefit. Sarah trusted him to know what to do when the time was right.

"You can let go of my hand now," she said petulantly. "You're crunching my knuckles together."

"I think it's better if we don't let go for the time being. This cell is larger than it seems."

"How's that?"

The Doctor inclined his head, lifting his ear into the air. "Listen to the echo of our voices. Listen to the wind, and the drip-drop of moisture far in the distance. I know dimensional transcendence when I feel it, and I feel it here in this very cell. This space is larger on the inside than it is on the outside."

Sarah swallowed. "So how are we supposed to get out of here?"

"We're not "supposed" to at all, Sarah Jane, that's rather the idea of a cell. The best the two of us can do is stick together and explore a bit. We can at least get away from the door, make finding us a little difficult."

"You're the Doctor."

Sarah could hear the smile on his lips. "The definite article, you might say."

The corner of her mouth curled into a tiny grin. Hand in hand, they began to walk into the darkness.

Their footsteps echoed around the indeterminably large chamber. Every breath was as loud as the lashing winds of a hurricane. The Doctor, for a while, contented himself with listening to the melody of the blood pumping in his ears and by counting his hearts-beat in rhythm with his steps. But Sarah said nothing as they walked on, and soon the Doctor found himself gasping for conversation like a fish out of water.

"Why is a raven like a writing desk, Sarah?"

She didn't answer him, and the Doctor took it to mean she was mulling it over in her mind.

"I'll give you a hint," he wheedled mischievously, "_Alice in Wonderland._ The Mad Hatter? No?"

Sarah was silent, her breathing too quiet to hear. The Doctor's strained gayety vanished in an instant.

"Sarah? Sarah, do say something. You're making me nervous."

The Doctor gave her hand another reassuring squeeze, and his long fingers fell through open air.

His eyes bugged in alarm. "Sarah! Sarah Jane, where are you? _Sarah!_"

He ran. The stone floor was uneven and slippery with thick rivulets of moisture, but the Doctor didn't slow. He cried out to Sarah in the dark, the echo of deep brass voice mocking him from the walls. He must have run into the outlet of the moisture, some sort of large puddle or pond, for soon he was no longer running but wading up to his knees in thick, viscous liquid.

"Surely she couldn't have wondered this far," he muttered, then bellowed, "_Sarah Jane Smith, where are you?!_"

_Where are you, where are you, where are you,_ his echo sang back.

The Doctor ground his teeth in frustration, dragging his feet and the ends of his scarf through the pond water. It was up to his waist now, its expanses much deeper and much larger than he had originally thought.

"I have to get through it." A manic energy seemed to beset him. "I have to find Sarah. I have to get through it!"

He tried parting the syrupy water with his hands. It clung to his fingers and the cuffs of his jacket. The entire pond, more of a lake now, reeked of something musty and sour. The water was uncomfortably warm, and the vapor that wrapped itself around the Doctor smelt of decay.

The Doctor's hands were sticky, his clothes clotted and stiff. In a sudden fit of curiosity, he put a single finger to his lips and tasted the water. It was not entirely unpleasant, not like the stagnant, salty pond filth he had expected. There was no definite flavor, _per se_, but a mere hint of something tangy, almost metallic . . .

The Doctor reeled back in horror. He tried to run, tried to get out, but it was like moving through treacle. The viscous fluid prevented him from taking a single step.

"Sarah!" he cried weakly. "Sarah, please . . ."

Something bumped his elbow as it floated on the surface of the bloody lake. The Doctor still could not see, but the object was soft and slippery from its long float. Using his sticky fingers, the Doctor touched it, tried to identify it. He felt matted hair and a cold forehead, eyeballs as smooth and dry as marbles, then a delicate nose broken in multiple places. The lips were slightly parted, though the mouth was filled with hot blood and flecks of broken teeth. He trailed his hands lower, over a small chin and down a slim neck. He stopped when his fingers found the mangled crevasse of flesh bisecting the smooth throat, where a plume of slick blood fountained into the lake.

The Doctor felt something break deep inside of him.

Sarah Jane's dead face twisted into a rictus grin, blood spurting from between the gaps in her teeth. The Doctor found that he could see her clearly, and wanted to claw his eyes out because of it.

"Don't gauge out those lovely blue eyes, Doctor," pleaded Sarah's corpse. "You'll ruin the only pretty feature you've got."

"Who . . ?" The Doctor trembled, unable to move. "What are you?"

"Just a shadow. An uncertainty that left you none the wiser."

"Are . . . are you real?"

"No, of course not," she retorted tartly, "but I'm the only reality you have left."

"You're not Sarah."

"Yes, I am, and I'll prove it. I first met you during a UNIT lockdown where I impersonated Aunt Lavinia and accused you of kidnapping all those scientists. You regenerated after you went back to the cave of the Great One, against my better wishes, at that! Our latest adventure was on Earth. We defeated Harrison Chase and the Krynoid and saved the day yet again! I am Sarah Jane Smith, and I died on this day in my own future, many miles below an alien planet, far away from home."

The Doctor saw himself reflected Sarah's pale, cataract eyes. His mirror image was distorted: his mouth was a thin red slash across his face, his teeth were pulled into a perpetual skeleton smile, and his blue eyes bulged out of the sockets of his skull. He looked away in disgust.

He asked quietly, "Why are you doing this?"

Sarah bobbed in the blood like a water buoy. The sight churned the Doctor insides. She replied, "I'm causing you pain, Doctor. It hurts you to see me like this."

"Yes. Obviously."

"Makes your emotions fire up, doesn't it? Seeing a dead friend."

The Doctor was acutely aware of the fact that his clothes were crusted with dried blood. "Gets the endorphins going."

"Exactly."

"Am I addressing a superior member of the Ventrarian race?"

The corpse's mouth bubbled with blood as it laughed, "No! You are addressing Sarah Jane Smith."

"You're lying. You don't sound like Sarah. You don't talk like her."

Sarah's dead eyes rolled in their sockets in a parody of annoyance. "I'm dead, what do you expect? Think about it, Doctor. Can a species unable to risk any emotion whatsoever be capable of as elaborate a lie as this?"

"No, I suppose not."

"Good boy. And are you actually in any pain right now? The Ventrarians warned you you would be."

The Doctor scowled at her patronizing tone. "No."

"Are you sure?"

"Yes! I'm sure I'd be the first to know if I were being physically tortured!"

Sarah's grey lips tutted. "Again . . . are you sure? During the course of this entire ordeal, since that Ventrarian guard left your cell, have you been sure of anything?"

"Are you suggesting that I _am_ in pain?"

"Perhaps you are in indescribable agony. Perhaps you are just dreaming."

"How?"

"How is any pain created?" Sarah gurgled, "When the victim is unaware of something that is about to strike out and bite them."

"So what you're saying is . . . I am not in pain until I am made aware of the fact?"

"A bit of an uncertainty principle in of itself."

"Old Werner would be turning over in his grave."

Sarah, as if to accentuate his point, rolled over slightly in the blood. "A bit of poetic irony, wouldn't you say? Try to save your own life, and you are, in effect, destroying it."

"But that's what you want, isn't it?" asked the Doctor. "You want me to save my life by acknowledging a pain I don't even know about. You said you were the only reality I had left, yes? What if you _are_ truly real? What if you are the one trying to save me from the grip of the Ventrarians, trying to free me?"

"That is your decision to make. A subatomic particle may exist as many different types of particles with varying velocities and atomic masses, hypothetically, until directly measured."

"Then . . ." The Doctor steeled himself, closed his great blue eyes, and bellowed into the sky,

"I DENY THIS REALITY!"

Then the pain came, and the Doctor screamed. And screamed. And screamed.

* * *

"Doctor! Oh my God, Doctor! Wake up! WAKE UP!"

Sarah Jane Smith clasped her hands in delight as her friend's bulgy blue eyeballs finally flew open. He tried sitting upright, but was stopped by a long needle embedded in a jack in the back of his neck.

"Like . . . _The Matrix_," murmured the Doctor blearily.

"Oh Doctor, I knew it would work! I knew if I shook you and prodded you long enough you'd eventually come round. Didn't half give me one hell of a fright, though." Sarah pressed hurriedly, "What happened down there?"

The Doctor looked a mite overwhelmed. He stared at her wide-eyed with bemusement. "It's rather difficult to explain, Sarah Jane."

"Well, never mind that now!" She helped him remove the needle. She twisted the plug with icy fingers until it slid away from the jack with a quiet sucking noise. The Doctor propped himself up on unsteady feet as his companion said, "We have to get out of here before our Ventrarian friends wake up!"

The Doctor raised an eyebrow. "How in the name of Jimi Hendrix did you get past them?"

"A crowbar is like a sonic screwdriver, Doctor. Keep it handy, give it a whirl, and suddenly all my problems are but ships passing in the night." Sarah hefted the huge metal instrument for emphasis. "Let's get out of here!"

The Doctor nodded hurriedly. He grasped Sarah's hand, her real hand, warm and soft and pulsing with a steady heartbeat and so wonderfully alive, and the two of them dashed outside to face a universe of terrors.

* * *

The Ventrarian favored his associate with a look that was utterly inscrutable. "Is this wise?"

"Specify," ordered the Other.

His colleague gestured to the prone body in front of them. "Letting the Time Lord believe he has escaped. He is happy. He rejoices in the knowledge of his companion's continued survival. He has purpose again now that he has her to protect. How are any of these developments productive to our cause?"

"Because," explained the Other, "the subject must believe entirely in the legitimacy of his scenario or the simulations are useless. His companion is a resourceful specimen, logically she would assist in an escape attempt were his phantasms indicative of reality. And . . . research has shown that the vigilante known as the Doctor lives a vagabond life fraught with terror, danger, heartbreak . . . circumstances which illicit fear and a slew of other emotions we can scarcely begin to comprehend."

"We let him live his life, then. Harvest his endorphin levels as he grows old, dies, regenerates, grows old, dies, _ad infinitum?_"

The Other inclined his head. "Of course. For what greater suffering is there him the Doctor, than for him to simply live on. Growing older, and more alone, as the years crumble away into oblivion . . . Forever."


End file.
